The Experts below are selected from a list of 10344 Experts worldwide ranked by ideXlab platform
Alberto Martilli - One of the best experts on this subject based on the ideXlab platform.
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a multi layer Urban Canopy meteorological model with trees bep tree street tree impacts on pedestrian level climate
urban climate, 2020Co-Authors: Scott E Krayenhoff, Alberto Martilli, Andreas Christen, Timothy Jiang, Brian N Bailey, Negin Nazarian, James A Voogt, Marco Giometto, Austine Stastny, Ben CrawfordAbstract:Abstract Vegetation alters Urban climates via transpirational cooling; however, unlike shorter vegetation, trees additionally provide shade and shelter. Urban Canopy models (UCMs) are coupled with mesoscale models for assessment of neighbourhood-scale climate, but their representation of Urban trees is limited. We present BEP-Tree, a multi-layer UCM that integrates trees instead of using the ‘tile’ approach that characterizes most Urban mesoscale modelling. BEP-Tree resolves the microclimate underneath trees where outdoor human thermal exposure occurs; these conditions are largely inaccessible to current mesoscale modelling and remote sensing approaches. Moreover, BEP-Tree allows trees to protrude above buildings, enabling assessment of low-rise neighbourhoods. The new model combines existing models, including detailed radiative and hydrodynamic models that assess built-tree interactions, and includes new parameterizations for impacts of tree foliage distribution. BEP-Tree is evaluated against unique datasets from three cities enabling assessment of modelled radiation, energy exchanges and road and air temperatures across the diurnal cycle. Urban trees redirect sensible heat into latent heat and reduce pedestrian-level solar radiation, wind, and temperatures during daytime. Thermal climate and energy exchanges are more sensitive to street tree density than height. Coupled with a mesoscale model, BEP-Tree enables assessment of Urban forest-induced neighbourhood-to-city scale climate impacts during fair weather periods.
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wudapt an Urban weather climate and environmental modeling infrastructure for the anthropocene
Bulletin of the American Meteorological Society, 2018Co-Authors: Jason Ching, Gerald Mills, Johan Feddema, Oscar Brousse, Petros Mouzourides, Alberto Martilli, Xuemei Wang, Benjamin Bechtel, Marina Neophytou, Iain D StewartAbstract:Capsule Summary:WUDAPT, an International community generated Urban Canopy information and modeling infrastructure (Portal) to facilitate Urban focused climate, weather, air quality, and energy use modeling application studies.
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on the anthropogenic heat fluxes using an air conditioning evaporative cooling parameterization for mesoscale Urban Canopy models
Journal of Solar Energy Engineering-transactions of The Asme, 2015Co-Authors: Estatio Gutierrez, Alberto Martilli, Jorge E Gonzalez, Robert BornsteinAbstract:An air conditioning evaporative cooling parameterization was implemented in a building effect parameterization/building energy model (BEP + BEM) to calculate the magnitude of the anthropogenic sensible and latent heat fluxes from buildings released to the atmosphere. The new heat flux formulation was tested in New York City (NYC) for the summer of 2010. Evaporative cooling technology diminishes between 80% and 90% of the anthropogenic sensible heat from air conditioning systems by transforming it into latent heat in commercial (COMM) areas over NYC. Average 2-m air temperature is reduced by 0.8 °C, while relative humidity is increased by 3% when cooling towers (CTs) are introduced. Additionally, CTs introduce stable atmospheric conditions in the Urban Canopy layer reducing turbulence production particularly during dry days.
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a double canyon radiation scheme for multi layer Urban Canopy models
Boundary-Layer Meteorology, 2012Co-Authors: Sebastian Schubert, Susanne Grossmanclarke, Alberto MartilliAbstract:We develop a double-canyon radiation scheme (DCEP) for Urban Canopy models embedded in mesoscale numerical models based on the Building Effect Parametrization (BEP). The new scheme calculates the incoming and outgoing longwave and shortwave radiation for roof, wall and ground surfaces for an Urban street canyon characterized by its street and building width, canyon length, and the building height distribution. The scheme introduces the radiative interaction of two neighbouring Urban canyons allowing the full inclusion of roofs into the radiation exchange both inside the canyon and with the sky. In contrast to BEP, we also treat direct and diffuse shortwave radiation from the sky independently, thus allowing calculation of the effective parameters representing the Urban diffuse and direct shortwave radiation budget inside the mesoscale model. Furthermore, we close the energy balance of incoming longwave and diffuse shortwave radiation from the sky, so that the new scheme is physically more consistent than the BEP scheme. Sensitivity tests show that these modifications are important for Urban regions with a large variety of building heights. The evaluation against data from the Basel Urban Boundary Layer Experiment indicates a good performance of the DCEP when coupled with the regional weather and climate model COSMO-CLM.
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a study of the Urban boundary layer using different Urban parameterizations and high resolution Urban Canopy parameters with wrf
Journal of Applied Meteorology and Climatology, 2011Co-Authors: Francisco Salamanca, Alberto Martilli, Mukul Tewari, Fei ChenAbstract:AbstractIn the last two decades, mesoscale models (MMs) with Urban Canopy parameterizations have been widely used to study Urban boundary layer processes. Different studies show that such parameterizations are sensitive to the Urban Canopy parameters (UCPs) that define the Urban morphology. At the same time, high-resolution UCP databases are becoming available for several cities. Studies are then needed to determine, for a specific application of an MM, the optimum degree of complexity of the Urban Canopy parameterizations and the resolution and details necessary in the UCP datasets. In this work, and in an attempt to answer the previous issues, four Urban Canopy schemes, with different degrees of complexity, have been used with the Weather Research and Forecasting (WRF) model to simulate the planetary boundary layer over the city of Houston, Texas, for two days in August 2000. For the UCP two approaches have been considered: one based on three Urban classes derived from the National Land Cover Data of th...
Zhihua Wang - One of the best experts on this subject based on the ideXlab platform.
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a single layer Urban Canopy model with transmissive radiation exchange between trees and street canyons
Building and Environment, 2021Co-Authors: Chenghao Wang, Zhihua Wang, Young-hee RyuAbstract:Abstract Urban trees are one of the most effective strategies to mitigate excessive heat stress in cities. To understand the underlying mechanisms of their cooling effect and to assess their use in Urban planning, the accurate simulation of how trees interact with the ambient built environment is critical and imperative. However, the representation of Urban trees in existing Urban Canopy models (in particular the single-layer ones) remains oversimplified. Here we develop a new Monte Carlo ray tracing method to explicitly resolve the Canopy transmittance and evaluate its impact on radiative view factors between trees and regular building facets. The new method is highly accurate in reproducing analytical solutions. Sensitivity tests of radiative view factors suggest the importance of Canopy transmittance in changing the radiation exchange. We then incorporate the ray tracing algorithm into the new version of the Arizona State University (ASU) Single-Layer Urban Canopy Model (ASLUM v3.1). In addition to radiation transmittance, ASLUM v3.1 explicitly resolves the radiative shading, evapotranspiration, and root water uptake of Urban trees in street canyons, with significantly improved performance in predictions (especially latent heat flux) when compared to previous versions. We further apply ASLUM v3.1 to evaluate the impacts of trees with varying characteristics on Urban radiation exchange and turbulent heat fluxes. Results show that Urban trees reduce the net radiation of ground and wall as well as the daytime temperature via shading and transpiration, but may slightly warm the nighttime street canyons through radiative trapping effect.
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Realistic Representation of Trees in an Urban Canopy Model
Boundary-Layer Meteorology, 2016Co-Authors: Elie Bou-zeid, Zhihua Wang, James A. SmithAbstract:A single-layer Urban Canopy model that captures sub-facet heterogeneity and various hydrological processes is further developed to explicitly incorporate trees within the Urban canyon. The physical processes associated with trees are shortwave/longwave radiation exchange, including mutual interception and shading by trees and buildings and multiple reflections, sensible heat and latent heat (through transpiration) exchange, and root water uptake. A computationally-efficient geometric approach is applied to the radiation exchanges, requiring a priori knowledge of view factors. These view factors are first obtained from independent Monte Carlo ray-tracing simulations, and subsequently simple relations, which are functions of canyon aspect ratio and tree-crown ratio, are proposed to estimate them. The developed model is evaluated against field observations at two Urban sites and one subUrban site, showing improved performance for latent heat flux compared to the previous version that only includes ground vegetation. The trees in the Urban Canopy act to considerably decrease sensible heat flux and increase latent heat flux, and these effects are found to be more significant in the more dense Urban site. Sensitivity tests are then performed to examine the effects of tree geometry relative to canyon geometry. The results indicate that the tree-crown size relative to canyon width is the most influential parameter to decrease sensible heat flux and increase latent heat flux, resulting in cooling of the Urban area.
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impacts of mesic and xeric Urban vegetation on outdoor thermal comfort and microclimate in phoenix az
Building and Environment, 2015Co-Authors: Jiyun Song, Zhihua WangAbstract:Abstract Urban vegetation is an effective way in mitigating excessive heat and improving the outdoor thermal environment for residents in cities via evaporative cooling. Different Urban vegetation forms (mesic or xeric) alter surface energy and water budgets in different ways, which is further complicated by interactions with buildings and anthropogenic controls. Mesic vegetation such as lawns reduces Urban temperatures by evaporative cooling but requires large amounts of water for continuous irrigation. On the other hand, xeric vegetation such as shade trees reduces Urban temperatures mainly through shading and has low water demand. The objective of this study is to investigate the impacts of different vegetation forms on microclimate in a hot desert city – Phoenix, AZ. We applied an advanced Urban Canopy model coupled with a single-column atmospheric model to simulate Urban boundary layer dynamics over different landscaping scenarios with different combinations of mesic and xeric vegetation forms. We subsequently compared the Urban land surface temperatures, near-surface air temperatures, outdoor thermal comfort in the Urban Canopy layer, as well as atmospheric dynamics (temperature, humidity) in the overlying boundary layer for a set of different scenarios.
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enhancing hydrologic modelling in the coupled weather research and forecasting Urban modelling system
Boundary-Layer Meteorology, 2015Co-Authors: Jiachuan Yang, Zhihua Wang, Mukul Tewari, Fei Chen, Shiguang Miao, James A Voogt, Soe W MyintAbstract:Urbanization modifies surface energy and water budgets, and has significant impacts on local and regional hydroclimate. In recent decades, a number of Urban Canopy models have been developed and implemented into the Weather Research and Forecasting (WRF) model to capture Urban land-surface processes. Most of these models are inadequate due to the lack of realistic representation of Urban hydrological processes. Here, we implement physically-based parametrizations of Urban hydrological processes into the single layer Urban Canopy model in the WRF model. The new single-layer Urban Canopy model features the integration of, (1) anthropogenic latent heat, (2) Urban irrigation, (3) evaporation from paved surfaces, and (4) the Urban oasis effect. The new WRF–Urban modelling system is evaluated against field measurements for four different cities; results show that the model performance is substantially improved as compared to the current schemes, especially for latent heat flux. In particular, to evaluate the performance of green roofs as an Urban heat island mitigation strategy, we integrate in the Urban Canopy model a multilayer green roof system, enabled by the physical Urban hydrological schemes. Simulations show that green roofs are capable of reducing surface temperature and sensible heat flux as well as enhancing building energy efficiency.
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interfacing the Urban land atmosphere system through coupled Urban Canopy and atmospheric models
Boundary-Layer Meteorology, 2015Co-Authors: Jiyun Song, Zhihua WangAbstract:We couple a single column model (SCM) to a cutting-edge single-layer Urban Canopy model (SLUCM) with realistic representation of Urban hydrological processes. The land-surface transport of energy and moisture parametrized by the SLUCM provides lower boundary conditions to the overlying atmosphere. The coupled SLUCM–SCM model is tested against field measurements of sensible and latent heat fluxes in the surface layer, as well as vertical profiles of temperature and humidity in the mixed layer under convective conditions. The model is then used to simulate Urban land–atmosphere interactions by changing Urban geometry, surface albedo, vegetation fraction and aerodynamic roughness. Results show that changes of landscape characteristics have a significant impact on the growth of the boundary layer as well as on the distributions of temperature and humidity in the mixed layer. Overall, the proposed numerical framework provides a useful stand-alone modelling tool, with which the impact of Urban land-surface conditions on the local hydrometeorology can be assessed via land–atmosphere interactions.
Shiguang Miao - One of the best experts on this subject based on the ideXlab platform.
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a new perspective on evaluating high resolution Urban climate simulation with Urban Canopy parameters
urban climate, 2021Co-Authors: Xuan Chen, Jiachuan Yang, Shiguang MiaoAbstract:Abstract The ‘state-of-the-art’ Urban climate models have not been evaluated against dense meteorological networks under various weather conditions. In this study, we conducted high-resolution Urban climate simulations in Beijing and investigated the relationship between their performances and Urban Canopy parameters (UCPs). The latest version of single-layer (UCM) and multi-layer (BEP) Urban Canopy models were tested separately. Results show that model performances are insensitive to rainfall events in summer, but change significantly with wind conditions in winter. Inclusion of UCPs has a limited impact on air temperature simulations. In terms of wind speed simulations, consistent overestimations by UCM and BEP are found in both summer and winter. The overestimation by BEP reduces significantly when UCPs are available, especially on windy days in winter. On the other hand, performance of UCM can degrade over Urban areas with Canopy parameters. Wind speed biases are found to correlate significantly with UCPs. The accuracy of wind speed simulations by UCM and BEP increases with Urban fraction and building surface ratio. This indicates poor model performances over low-density Urban areas, which requires enhanced aerodynamic parameterizations to better account for UCPs. This study reveals the limitation of current Urban climate simulations and provides guidance for future model developments.
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sensitivity of Urban boundary layer simulation to Urban Canopy models and pbl schemes in beijing
Meteorology and Atmospheric Physics, 2019Co-Authors: Meng Huang, Fei Chen, Zhiqiu Gao, Shiguang MiaoAbstract:Mesoscale models with Urban Canopy models (UCM) have been increasingly used to study Urban boundary layer processes. Using the data from a high-resolution Doppler lidar, automatic weather stations (AWS), and a flux tower located in the Urban site, we assessed the performance of the Urbanized Weather Research and Forecasting (WRF) model through three Urban Canopy models (the single-layer UCM, and the multi-layer BEP and BEM models) and four planetary boundary layer (PBL) schemes (the non-local first-order YSU, SH and ACM2 schemes, as well as the local TKE-based BouLac scheme) for one cloudy and one clear sky days. Results show that the WRF-Urban generally overestimates the sensible heat flux and underestimates the latent heat flux. The simulated 2-m temperature and 10-m wind speed are more sensitive to UCMs than to PBL schemes. Using the BouLac PBL scheme and the multi-layer BEP generates the best agreement with AWS observations. Simulations with the multi-layer BEM produce the highest mixing-layer heights. The convective boundary layer (CBL) from the single-layer UCM experiment develops at the slowest pace when compared with other two multi-layer UCMs. When the single-layer UCM is used, simulations with the non-local mixing YSU, SH and ACM2 schemes perform better than the TKE-based scheme (BouLac) for representing the CBL structure. Additionally, the scale-aware SH scheme considering the effect of grid resolution on the vertical dimension, simulates the potential temperature profiles that are closest to observations.
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high resolution dataset of Urban Canopy parameters for beijing and its application to the integrated wrf Urban modelling system
Journal of Cleaner Production, 2019Co-Authors: Xinran Wang, Liang Chen, Yizhou Zhang, Shiguang MiaoAbstract:Abstract The Weather Research and Forecasting (WRF) model with Urban Canopy model has been widely used to study atmospheric boundary layer processes and Urbanization-related environmental issues. One of the most daunting challenges faced by the integrated WRF/Urban modelling system is constraining the uncertainties in Urban Canopy parameters (UCPs) that represent the Urban morphological characteristics. In this paper, we develop a dataset of three-dimensional (3-D) UCPs for Beijing by using vector-format building information in a Geographic Information System (GIS) environment and apply it to the integrated WRF/Urban modelling system to investigate the effects of UCPs on the simulated meteorological variables against observations in clear-sky days. Moreover, the role of spatially-varying UCPs involved in the Building Effect Parameterization (BEP) in capturing the heterogeneous characteristics of 2-m surface air temperature and 10-m wind field in the Urban areas are evaluated. In general, high-resolution dataset of UCPs improves the model skill in simulating the diurnal variations and spatial distributions of 2-m surface air temperature and 10-m wind speed in the Urban Canopy, especially for the BEP. WRF/BEP with gridded UCPs dataset shows a better performance in densely built-up areas, where the morphological and physical characteristics of Urban surface are complex. It also performs better in capturing the characteristics of Urban heat islands (UHIs) and weak wind zones (WWZs) in Urban areas. Results show that introducing the 3-D UCPs dataset into the integrated WRF/Urban modelling system is a simple and yet efficient way to enhance the modelling capabilities in Urban areas and assist Urban planners to deal with Urban environmental issues.
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enhancing hydrologic modelling in the coupled weather research and forecasting Urban modelling system
Boundary-Layer Meteorology, 2015Co-Authors: Jiachuan Yang, Zhihua Wang, Mukul Tewari, Fei Chen, Shiguang Miao, James A Voogt, Soe W MyintAbstract:Urbanization modifies surface energy and water budgets, and has significant impacts on local and regional hydroclimate. In recent decades, a number of Urban Canopy models have been developed and implemented into the Weather Research and Forecasting (WRF) model to capture Urban land-surface processes. Most of these models are inadequate due to the lack of realistic representation of Urban hydrological processes. Here, we implement physically-based parametrizations of Urban hydrological processes into the single layer Urban Canopy model in the WRF model. The new single-layer Urban Canopy model features the integration of, (1) anthropogenic latent heat, (2) Urban irrigation, (3) evaporation from paved surfaces, and (4) the Urban oasis effect. The new WRF–Urban modelling system is evaluated against field measurements for four different cities; results show that the model performance is substantially improved as compared to the current schemes, especially for latent heat flux. In particular, to evaluate the performance of green roofs as an Urban heat island mitigation strategy, we integrate in the Urban Canopy model a multilayer green roof system, enabled by the physical Urban hydrological schemes. Simulations show that green roofs are capable of reducing surface temperature and sensible heat flux as well as enhancing building energy efficiency.
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enhanced modeling of latent heat flux from Urban surfaces in the noah single layer Urban Canopy coupled model
Science China-earth Sciences, 2014Co-Authors: Shiguang Miao, Fei ChenAbstract:The numerical modeling of the impacts of Urban buildings in mesoscale meteorological models has gradually improved in recent years. Correctly representing the latent heat flux from Urban surfaces is a key issue in Urban land-atmosphere coupling studies but is a common weakness in current Urban Canopy models. Using the surface energy balance data at a height of 140 m from a 325 m meteorological tower in Beijing, we conducted a 1-year continuous off-line simulation by using a coupled land surface model and a single-layer Urban Canopy model and found that this model has a relatively large systematic error for simulated latent heat flux. To improve the numerical method for modeling latent heat flux from Urban surfaces, we combined observational analysis and Urban land surface model to derive an oasis effect coefficient for Urban green areas; to develop a temporal variation formula for water availability in Urban impervious surfaces; and to specify a diurnal profile and the maximum values of anthropogenic latent heat release for four seasons. These results are directly incorporated into the Urban land surface model to improve model performance. In addition, this method serves as a reference for studies in other Urban areas.
Fei Chen - One of the best experts on this subject based on the ideXlab platform.
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sensitivity of Urban boundary layer simulation to Urban Canopy models and pbl schemes in beijing
Meteorology and Atmospheric Physics, 2019Co-Authors: Meng Huang, Fei Chen, Zhiqiu Gao, Shiguang MiaoAbstract:Mesoscale models with Urban Canopy models (UCM) have been increasingly used to study Urban boundary layer processes. Using the data from a high-resolution Doppler lidar, automatic weather stations (AWS), and a flux tower located in the Urban site, we assessed the performance of the Urbanized Weather Research and Forecasting (WRF) model through three Urban Canopy models (the single-layer UCM, and the multi-layer BEP and BEM models) and four planetary boundary layer (PBL) schemes (the non-local first-order YSU, SH and ACM2 schemes, as well as the local TKE-based BouLac scheme) for one cloudy and one clear sky days. Results show that the WRF-Urban generally overestimates the sensible heat flux and underestimates the latent heat flux. The simulated 2-m temperature and 10-m wind speed are more sensitive to UCMs than to PBL schemes. Using the BouLac PBL scheme and the multi-layer BEP generates the best agreement with AWS observations. Simulations with the multi-layer BEM produce the highest mixing-layer heights. The convective boundary layer (CBL) from the single-layer UCM experiment develops at the slowest pace when compared with other two multi-layer UCMs. When the single-layer UCM is used, simulations with the non-local mixing YSU, SH and ACM2 schemes perform better than the TKE-based scheme (BouLac) for representing the CBL structure. Additionally, the scale-aware SH scheme considering the effect of grid resolution on the vertical dimension, simulates the potential temperature profiles that are closest to observations.
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enhancing hydrologic modelling in the coupled weather research and forecasting Urban modelling system
Boundary-Layer Meteorology, 2015Co-Authors: Jiachuan Yang, Zhihua Wang, Mukul Tewari, Fei Chen, Shiguang Miao, James A Voogt, Soe W MyintAbstract:Urbanization modifies surface energy and water budgets, and has significant impacts on local and regional hydroclimate. In recent decades, a number of Urban Canopy models have been developed and implemented into the Weather Research and Forecasting (WRF) model to capture Urban land-surface processes. Most of these models are inadequate due to the lack of realistic representation of Urban hydrological processes. Here, we implement physically-based parametrizations of Urban hydrological processes into the single layer Urban Canopy model in the WRF model. The new single-layer Urban Canopy model features the integration of, (1) anthropogenic latent heat, (2) Urban irrigation, (3) evaporation from paved surfaces, and (4) the Urban oasis effect. The new WRF–Urban modelling system is evaluated against field measurements for four different cities; results show that the model performance is substantially improved as compared to the current schemes, especially for latent heat flux. In particular, to evaluate the performance of green roofs as an Urban heat island mitigation strategy, we integrate in the Urban Canopy model a multilayer green roof system, enabled by the physical Urban hydrological schemes. Simulations show that green roofs are capable of reducing surface temperature and sensible heat flux as well as enhancing building energy efficiency.
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enhanced modeling of latent heat flux from Urban surfaces in the noah single layer Urban Canopy coupled model
Science China-earth Sciences, 2014Co-Authors: Shiguang Miao, Fei ChenAbstract:The numerical modeling of the impacts of Urban buildings in mesoscale meteorological models has gradually improved in recent years. Correctly representing the latent heat flux from Urban surfaces is a key issue in Urban land-atmosphere coupling studies but is a common weakness in current Urban Canopy models. Using the surface energy balance data at a height of 140 m from a 325 m meteorological tower in Beijing, we conducted a 1-year continuous off-line simulation by using a coupled land surface model and a single-layer Urban Canopy model and found that this model has a relatively large systematic error for simulated latent heat flux. To improve the numerical method for modeling latent heat flux from Urban surfaces, we combined observational analysis and Urban land surface model to derive an oasis effect coefficient for Urban green areas; to develop a temporal variation formula for water availability in Urban impervious surfaces; and to specify a diurnal profile and the maximum values of anthropogenic latent heat release for four seasons. These results are directly incorporated into the Urban land surface model to improve model performance. In addition, this method serves as a reference for studies in other Urban areas.
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numerical simulation of Urban heat island effect by the wrf model with 4 km grid increment an inter comparison study between the Urban Canopy model and slab model
Journal of the Meteorological Society of Japan, 2012Co-Authors: Hiroyuki Kusaka, Mukul Tewari, Fei Chen, Jimy Dudhia, David O Gill, Michael G Duda, Wei Wang, Yukako MiyaAbstract:The present study applies the WRF model involving the single-layer Urban Canopy model (hereafter, WRF_UCM) to Urban climate simulation of the Tokyo metropolitan area for August (2004–2007) and compare results to (a) observations, and (b) the WRF model involving the slab Urban model (hereafter, WRF_SLAB). In this Urban area, WRF_UCM accurately captures the observed monthly mean daytime and nocturnal UHI, whereas WRF_SLAB does not show a nocturnal UHI. Moreover, the observed diurnal variations of the surface air temperature for central Tokyo and Kumagaya, a nearby inland city, are reproduced well by WRF_UCM. However, WRF_SLAB exhibits both a 1-hr phase shift and a 6.2 � C excess oscillation magnitude over observations. In addition, WRF_UCM accurately reproduces the frequency distribution of surface air temperatures, showing a maximum at 27 � C, whereas WRF_SLAB produce a bimodal distribution, with double peaks at 23 and 33 � C. Finally, WRF_UCM does a much better job than WRF_SLAB at modeling the relative humidity.
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a study of the Urban boundary layer using different Urban parameterizations and high resolution Urban Canopy parameters with wrf
Journal of Applied Meteorology and Climatology, 2011Co-Authors: Francisco Salamanca, Alberto Martilli, Mukul Tewari, Fei ChenAbstract:AbstractIn the last two decades, mesoscale models (MMs) with Urban Canopy parameterizations have been widely used to study Urban boundary layer processes. Different studies show that such parameterizations are sensitive to the Urban Canopy parameters (UCPs) that define the Urban morphology. At the same time, high-resolution UCP databases are becoming available for several cities. Studies are then needed to determine, for a specific application of an MM, the optimum degree of complexity of the Urban Canopy parameterizations and the resolution and details necessary in the UCP datasets. In this work, and in an attempt to answer the previous issues, four Urban Canopy schemes, with different degrees of complexity, have been used with the Weather Research and Forecasting (WRF) model to simulate the planetary boundary layer over the city of Houston, Texas, for two days in August 2000. For the UCP two approaches have been considered: one based on three Urban classes derived from the National Land Cover Data of th...
Hiroyuki Kusaka - One of the best experts on this subject based on the ideXlab platform.
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impact of an improved wrf Urban Canopy model on diurnal air temperature simulation over northern taiwan
Atmospheric Chemistry and Physics, 2016Co-Authors: Chuanyao Lin, Hiroyuki Kusaka, Yuko Akimoto, Yang Fan Sheng, J C Huang, Huanghsiung HsuAbstract:Abstract. This study evaluates the impact of Urbanization over northern Taiwan using the Weather Research and Forecasting (WRF) Model coupled with the Noah land-surface model and a modified Urban Canopy model (WRF–UCM2D). In the original UCM coupled to WRF (WRF–UCM), when the land use in the model grid is identified as "Urban", the Urban fraction value is fixed. Similarly, the UCM assumes the distribution of anthropogenic heat (AH) to be constant. This may not only lead to over- or underestimation of Urban fraction and AH in Urban and non-Urban areas, but spatial variation also affects the model-estimated temperature. To overcome the abovementioned limitations and to improve the performance of the original UCM model, WRF–UCM is modified to consider the 2-D Urban fraction and AH (WRF–UCM2D). The two models were found to have comparable temperature simulation performance for Urban areas, but large differences in simulated results were observed for non-Urban areas, especially at nighttime. WRF–UCM2D yielded a higher correlation coefficient (R2) than WRF–UCM (0.72 vs. 0.48, respectively), while bias and RMSE achieved by WRF–UCM2D were both significantly smaller than those attained by WRF–UCM (0.27 and 1.27 vs. 1.12 and 1.89, respectively). In other words, the improved model not only enhanced correlation but also reduced bias and RMSE for the nighttime data of non-Urban areas. WRF–UCM2D performed much better than WRF–UCM at non-Urban stations with a low Urban fraction during nighttime. The improved simulation performance of WRF–UCM2D in non-Urban areas is attributed to the energy exchange which enables efficient turbulence mixing at a low Urban fraction. The result of this study has a crucial implication for assessing the impacts of Urbanization on air quality and regional climate.
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numerical simulation of Urban heat island effect by the wrf model with 4 km grid increment an inter comparison study between the Urban Canopy model and slab model
Journal of the Meteorological Society of Japan, 2012Co-Authors: Hiroyuki Kusaka, Mukul Tewari, Fei Chen, Jimy Dudhia, David O Gill, Michael G Duda, Wei Wang, Yukako MiyaAbstract:The present study applies the WRF model involving the single-layer Urban Canopy model (hereafter, WRF_UCM) to Urban climate simulation of the Tokyo metropolitan area for August (2004–2007) and compare results to (a) observations, and (b) the WRF model involving the slab Urban model (hereafter, WRF_SLAB). In this Urban area, WRF_UCM accurately captures the observed monthly mean daytime and nocturnal UHI, whereas WRF_SLAB does not show a nocturnal UHI. Moreover, the observed diurnal variations of the surface air temperature for central Tokyo and Kumagaya, a nearby inland city, are reproduced well by WRF_UCM. However, WRF_SLAB exhibits both a 1-hr phase shift and a 6.2 � C excess oscillation magnitude over observations. In addition, WRF_UCM accurately reproduces the frequency distribution of surface air temperatures, showing a maximum at 27 � C, whereas WRF_SLAB produce a bimodal distribution, with double peaks at 23 and 33 � C. Finally, WRF_UCM does a much better job than WRF_SLAB at modeling the relative humidity.
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trade offs and responsiveness of the single layer Urban Canopy parametrization in wrf an offline evaluation using the moscem optimization algorithm and field observations
Quarterly Journal of the Royal Meteorological Society, 2010Co-Authors: Thomas Loridan, Hiroyuki Kusaka, Alberto Martilli, Mukul Tewari, Fei Chen, Susanne Grossmanclarke, C S B Grimmond, Kevin W Manning, Martin BestAbstract:For an increasing number of applications, mesoscale modelling systems now aim to better represent Urban areas. The complexity of processes resolved by Urban parametrization schemes varies with the application. The concept of fitness-for-purpose is therefore critical for both the choice of parametrizations and the way in which the scheme should be evaluated. A systematic and objective model response analysis procedure (Multiobjective Shuffled Complex Evolution Metropolis (MOSCEM) algorithm) is used to assess the fitness of the single-layer Urban Canopy parametrization implemented in the Weather Research and Forecasting (WRF) model. The scheme is evaluated regarding its ability to simulate observed surface energy fluxes and the sensitivity to input parameters. Recent amendments are described, focussing on features which improve its applicability to numerical weather prediction, such as a reduced and physically more meaningful list of input parameters. The study shows a high sensitivity of the scheme to parameters characterizing roof properties in contrast to a low response to road-related ones. Problems in partitioning of energy between turbulent sensible and latent heat fluxes are also emphasized. Some initial guidelines to prioritize efforts to obtain Urban land-cover class characteristics in WRF are provided. Copyright © 2010 Royal Meteorological Society and Crown Copyright.
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coupled wrf unified noah Urban Canopy modeling system
2007Co-Authors: Mukul Tewari, Hiroyuki Kusaka, Fei Chen, Shiguang MiaoAbstract:In order to better represent the physical processes involved in the exchange of heat, momentum, and water vapor in Urban environment in mesoscale model, an UCM is coupled to the WRF model. The main purpose of the coupled model is to improve the description of lower boundary conditions and to provide more accurate forecasts for Urban regions. The UCM is a single layer model which has a simplified Urban geometry. Some of the features of the UCM include, shadowing from buildings, reflection of short and longwave radiation, wind profile in the Canopy layer and multi-layer heat transfer equation for roof, wall and road surfaces (Kusaka and Kimura, JAM, 2004).
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thermal effects of Urban canyon structure on the nocturnal heat island numerical experiment using a mesoscale model coupled with an Urban Canopy model
Journal of Applied Meteorology, 2004Co-Authors: Hiroyuki Kusaka, Fujio KimuraAbstract:Abstract A single-layer Urban Canopy model is incorporated into a simple two-dimensional atmospheric model in order to examine the individual impacts of anthropogenic heating, a large heat capacity, and a small sky-view factor on mesoscale heat island formation. It is confirmed that a nocturnal heat island on a clear, calm summer day results from the difference in atmospheric stability between a city and its surroundings. The difference is caused by anthropogenic heating and the following two effects of Urban canyon structure: (i) a larger heat capacity due to the walls and (ii) a smaller sky-view factor. Sensitivity experiments show that the anthropogenic heating increases the surface air temperature though the day. (This factor strongly affects the nocturnal temperature, and the maximum increase of 0.67°C occurs at 0500 LST.) The larger heat capacity due to the walls decreases the daytime temperature and increases the nocturnal temperature. (The maximum increase of 0.39°C occurs at 0600 LST.) The smalle...
